U.S. patent number 4,296,304 [Application Number 05/943,798] was granted by the patent office on 1981-10-20 for electrode displacement monitoring in resistance welding.
This patent grant is currently assigned to Centre de Recherches Metallurgiques-Centrum voor Research in de. Invention is credited to Jacques Defourny.
United States Patent |
4,296,304 |
Defourny |
October 20, 1981 |
Electrode displacement monitoring in resistance welding
Abstract
One or two sensors are used to measure the displacement of a
pair of electrodes relative to each other during resistance
welding. The axis of the or each sensor is parallel to and as close
as possible to the common alignment axis of the electrodes.
Inventors: |
Defourny; Jacques (Herstal,
BE) |
Assignee: |
Centre de Recherches
Metallurgiques-Centrum voor Research in de (Brussels,
BE)
|
Family
ID: |
19728702 |
Appl.
No.: |
05/943,798 |
Filed: |
September 19, 1978 |
Foreign Application Priority Data
Current U.S.
Class: |
219/86.41;
219/91.1; 219/110 |
Current CPC
Class: |
B23K
11/253 (20130101) |
Current International
Class: |
B23K
11/25 (20060101); B23K 011/10 () |
Field of
Search: |
;219/86.41,86.51,86.61,91.1,110 ;324/207,208 ;33/143F |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Rubinson; Gene Z.
Assistant Examiner: George; Keith E.
Attorney, Agent or Firm: Holman & Stern
Claims
I claim:
1. In combination with a resistance welding machine comprising a
main welding machine frame structure supporting a pair of first and
second electrodes having a common alignment axis, apparatus for
monitoring the operation of the welding machine, the apparatus
comprising:
a single sensor for measuring displacement of the electrodes
relative to each other during welding, the sensor having an axis
along which the said displacement is measured, the said axis of the
sensor and said common alignment axis of the electrodes being
mutually parallel, the distance between the said axes being
sufficiently small to render negligible any inadvertent small
variation in parallelism between said sensor axis and said common
alignment axis, wherein said single sensor is fixed to the first
electrode,
the apparatus further comprising a second frame member, separate
from said main frame structure and having two transverse elements,
which are substantially perpendicular to the said alignment axis,
and a longitudinal element interconnecting the transverse elements,
one of the transverse elements being fixed to the second electrode,
the other of the transverse elements being connected to the sensor,
the longitudinal element being spaced from the electrodes by a
distance which is only slightly less than the spacing between the
electrodes and the main welding machine frame.
2. Apparatus as claimed in claim 1, in which the frame has high
rigidity in the direction of movement of the electrodes, the
apparatus further comprising means for compressing the second frame
member perpendicularly to the alignment axis towards the first
electrode, against which the second frame member bears, in order to
prevent undesirable movement of the frame.
3. Apparatus as claimed in either of claims 1 or 2, in which the
sensor comprises an induction coil.
Description
FIELD OF THE INVENTION
The present invention relates to apparatus for "monitoring" the
welding of products, such as steel bar, steel sheet, and even
certain steel sections.
BACKGROUND OF THE INVENTION
The aim is to enable the quality of welding to be monitored while
welding is actually being carried out, and thus to enable the
welding conditions to be immediately modified so as to improve the
quality of welding if this is seen to be defective.
For achieving this aim I have already proposed an apparatus, more
specifically a sensor (preferably an induction sensor) by means of
which the relative displacement of welding electrodes can be
measured as a function of time, that is to say either the
penetration of the bars into one another or the expansion of the
sheets at the welding point can be measured by this sensor. The
curve thus obtained can be considered as the physical result of
interaction of the various operating values (current strength,
force at the electrodes, welding time) and, on this basis, as a
genuine output value on which any regulation of the welding process
can be based.
I have also proposed equipment which comprises, considered singly
or in combination:
a sensor by means of which the electrical energy dissipated during
the welding operation can be measured as a function of time,
a sensor by means of which the pressure applied to the two welding
electrodes can be measured, as a function of time, by any suitable
means
a sensor by means of which the speed of relative movement of the
electrodes can be measured, as a function of time, that is to say
by means of which it is possible to measure either the speed of
penetration of steel bars into one another or the speed of
expansion of sheet steels at the welding point.
The results obtained with this equipment have been found to be very
satisfactory but, in certain cases, the installation of the
movement sensor entails difficulties either due to the large amount
of space occupied or by reason by disturbances in the measurement
carried out.
Underlying the present invention is the object of providing an
apparatus by means of which these drawbacks can be remedied.
SUMMARY OF THE INVENTION
The apparatus of the present invention, for monitoring the
operations of a welding machine--which is principally composed of
an approximately U-shaped frame, of at least one pair of connection
electrodes, together with means for supplying these electrodes with
electrical energy and with means for applying pressure to these
electrodes, each pair of electrodes comprising at least one sensor,
which is preferably constituted by an induction coil by means of
which the relative displacement of the electrodes can be measured,
as a function of time, during welding--is characterised in that the
axis along which the movement is measured by the sensor is parallel
to the axis of alignment of the upper and lower electrodes
concerned, and the distance between the axis of the sensor and the
said alignment axis of the electrodes concerned is as small as
possible.
If there is a single sensor per pair of electrodes, one may be
ensured that the distance between the axis of the sensor and the
alignment axis of the electrodes concerned will be as small as
possible by connecting the sensor, which is fast with one
electrode, to the other electrode through the intermediary of a
frame having two elements which lie substantially perpendicularly
to the alignment axis of these electrodes and are interconnected by
a longitudinal element skirting the frame of the welding machine at
the greatest possible distance from the electrodes.
It is to be observed that a frame of this kind may be the seat of
vibrations which, when they have a component parallel to the
alignment axis of the electrodes, are the cause of significant
errors in the measurement of the relative movement of the
electrodes. Accordingly, it is advantageous with a view to
eliminating any chance of error, if the frame has high rigidity in
the direction of movement of the electrodes and, also, is equipped
with a compression system acting perpendicularly to the direction
of the said electrodes, against which the said frame bears, so as
to thereby eliminate any possibility of spurious or parasitic
displacement of the said frame.
If there are two displacement measuring sensors per pair of
electrodes, each sensor is fast with an electrode and effects
measurement of displacement of an electrode relative to a fixed
point, the relative displacement of the two electrodes being the
difference between these two measurements.
If such provisions are adopted, it will be ensured that there will
be no obstruction in the vicinity of the electrodes, which is of
particular value in instances where sheet steel components of large
size are to be welded, and it is thus ensured that no disturbances
will be caused to the measurements due to the axes of the
electrodes being misaligned with each other.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 diagrammatically illustrates a resistance welding machine in
which a single displacement measuring sensor is used per pair of
electrodes;
FIG. 2 diagrammatically illustrates an embodiment similar to that
of FIG. 1 but with the addition of an anti-vibration frame; and
FIG. 3 diagrammatically illustrates an embodiment in which two
displacement measuring sensors are used per pair of electrodes.
DESCRIPTION OF PREFERRED EMBODIMENTS
Referring first to FIG. 1, three sheet metal elements 1, 2, 3 are
welded together by means of electrodes 4 and 5, shown with their
respective electrode holders 6 and 7. A sensor 8, serving to
measure relative displacement of the electrodes, is fixed to the
electrode holder 6 by a strap 9 and is arranged in such a way that
the distance between the axis 10 of alignment of the electrodes 4
and 5 and the axis 11 of the sensor 8 is as small as possible and
in such a way that these axes 10, 11 are mutually parallel. The
sensor 8 is connected to the other electrode holder 7 through the
intermediary of a U-frame, whose two shanks 12 and 13 extend
substantially perpendicular to the axis 10 of alignment of the
electrode, the element 14 bridging and interconnecting the two
shanks 12 and 13 skirting the frame 15 of the welding machine as
far away as possible from the electrodes.
In the arrangement shown in FIG. 2, two sheet metal elements 16 and
17 are welded together by means of electrodes 18 and 19, which are
shown with their associated electrodes holders 20 and 21
respectively and with supports 22 and 23 respectively of the
electrode holders 20 and 21. A sensor 24, used for measuring
relative displacement of the electrodes 18 and 19 is fixed to
electrode 18 by way of a support 25, the support 22, and the
electrode holder 20, and is also fixed to the electrode 19 by way
of an anti-vibration frame 26, a support 27 used for securing the
frame 26 in place, the support 23, and the electrode holder 21.
The frame 26 is of tubular construction and is characterised by its
lightness and by its high degree of rigidity in the direction of
movement of the electrodes 18 and 19. The lower end of frame 26 is
received in a recess 28 in the support 27 and is secured in place
by means of a retaining system 29. The upper end of frame 26 bears
against the electrode holder 20 through the intermediary of an
element 30 made of an insulating material (Teflon for example)
which functions with low friction. In this way any spurious or
parasitic movement of the frame 26 is eliminated. The compression
component of the frame 26 is constituted by the torque indicated in
the drawing by arrow 31. This torque is applied as soon as the
frame is locked in the retaining system 29. This torque, applied to
the lower end of the frame, results in a compression force,
indicated by arrow 32, being applied between the element 30 at the
upper end of frame and electrode holder 20. This compression force
opposes any spurious or parasitic movement of the upper end of the
frame relative to the electrode holder 20.
In the arrangement shown in FIG. 3, two sheet metal elements 33 and
34 are welded together by means of electrodes 35 and 36, which are
shown with their associated electrode holders 37 and 38
respectively. Sensors 39 and 40, serving to measure relative
movement of the electrodes, are fixed to the associated electrode
holders 37 and 38 respectively through the intermediary of straps
41 and 42 respectively, so that the distances between the alignment
axis 43 of the electrodes and the axes 44 and 44bis of the sensors
39 and 40 are as small as possible, while the axis 43 is parallel
to the axes 44 and 44bis. The sensor 39 measures movement of
electrode 35 relative to a fixed point 45, and the sensor 40
carries out the same measurement for movement of electrode 36
relative to a fixed point 46. A value for relative displacement of
the two electrodes 35 and 36 is obtained by the difference between
the two measurement values.
* * * * *